buffre is used to reduce the delay(isolates two parts)........where as driver, drives the network (for that we need to choose different drive capabilities based on load).
Added after 3 minutes:
to construct a driver you need to set the transistor sizes and you can find theory on driver design from any vlsi design book
One more difference i would like mention between clock buffer and ordinary buffer ,i.e.
Clock net has high fan out when compared to orther ,so the drive strenght of clock buffer than that of an ordinary buffer must be high.